The present invention concerns a paper cushioning mat for packaging.
As cushioning materials for packaging there has been widely used foamed plastics such as foamed polystyrene in the form of molded blocks or discrete particles. Foamed plastics products are, however, kept at a distance by the customers because, when buried in the earth, they do not naturally decompose, and when burned in a conventional incinerator, they give irritating smell and black smoke.
The inventors intended to replace cushioning materials made of foamed plastics with those made of paper, and proposed a cushioning material made by rolling up a single faced corrugated fiberboard to a coil and a cushioning material made by further cutting the coil crosswise to round slices of a certain thickness (Japanese Utility Model Disclosure No.05-13966). Then, they proposed use of laminated products of a single faced corrugated fiberboard cut into small discrete particles, and the products made by fixing the laminates on a substrate (Japanese Patent Application No.03-355305).
The cushioning materials made by cutting single faced corrugated paper fiberboard products are, however, not suitable for packaging precision machines or electronic parts due to the paper dust formed by cutting. Further, apparent densities of laminated products of single faced corrugated fiberboard are such a high value. For example, that of "flute-A" which is used most widely is about 100 kg/m.sup.3, and thus, even the above discrete cushioning material has such a high apparent density as about 20 kg/m.sup.3, which is still high enough when compared with the apparent densities of foamed polystyrene products, about 9 kg/m.sup.3. In order to make the cushioning materials lighter efforts were made to use a paper of lower basic weight or to reduce the amount of adhesives used. These trials, however, gave no practical solutions because of lowered strength of the material Single faced corrugated fiberboard.